Future telecommunication systems may require power transfer between power distribution system and electronic cards through magnetic coupling for the following reasons:
(1) increased system reliability
(a) inherent short-circuit protection at the power interface (fuse-less protection) PA1 (b) limited power transfer to the load (elimination of fire hazard) PA1 (i) each AC/DC converter requires a fuse for short-circuit protection; and PA1 (ii) electrical connectors are required to feed power from power distribution circuit to the electronic cards. PA1 (i) square wave voltage in the distribution which results in high EMI; PA1 (ii) high voltage surges in the system under open circuit fault conditions; and PA1 (iii) poor distribution efficiency at reduced load power demand.
(2) compatibility with electrical connector-less interface (using fiber optical connectors for the signals) in the system.
In order to achieve magnetic coupling, the power distribution system should be of AC type. Furthermore, to reduce the size and volume of the power conversion units, the distribution frequency should be high.
The concept of high frequency power distribution systems was first proposed by NASA some 25 years ago for space applications. Since then, the industry has been working to exploit the potential of this concept for several other applications because of the following features:
high end-to-end system efficiency
distributed heat
hot insertion of electronic cards without active current limiting
point-of-use-regulation.
The following articles describe typical known power distribution systems:
[1] Status of 20 kHz space station power distribution technology, NASA Publication, TM 100781;
[2] Advanced secondary power system for transport aircraft, NASA Publication, TP 2463;
[3] B. Ray and T. A. Stuart, "A cascaded Schwarz converter for high frequency power distribution", IEEE Transactions on Power Electronics, Vol. 4, No. 4, Oct. 1989; and
[4] A. Kelley and W. Owens, "Connectorless power supply for an aircraft-passenger entertainment system", IEEE Transactions on
Power Electronics, Vol. 4, No. 3, July 1989.
There are two types of high frequency distribution systems described in literature and known in industry and FIGS. 1 and 2 of the accompanying drawings illustrate respectively these prior art systems:
(1) High Frequency Sinusoidal Constant Voltage Distribution System; and
(2) High Frequency Sinusoidal Constant Current Distribution System.